The present invention relates to a cylinder head and piston configuration of an internal combustion engine, and more particularly relates to such a configuration which incorporates a squish area.
In spark ignition type internal combustion engines, it is well known that the shape of the combustion chamber and relative positions of the spark plug and intake and exhaust ports have considerable effect on the combustion of the mixture gas, and modifying the shape of the combustion chamber and the relative positions of the spark plug and the intake and exhaust ports is effective for improving engine performance parameters, such as output power, fuel consumption, silence of operation, quality of exhaust gases, and so forth. Important goals in modifying these factors are shortening the flame propagation distance, increasing combustion velocity by imparting desirable turbulance to the mixture gas during the latter half of the compression stroke, reducing the temperature rise of the end gas, so as to suppress knocking, and so forth.
In order to increase combustion velocity, squish is utilized in many internal combustion engines. This introduces swirling motion to the mixture gases, mainly in the radial direction of the cylinder bore, and is obtained by forming a squish region between a planar region on an upper part of the piston and a planar region on a lower part of the cylinder head. The planar regions approach one another closely when the piston is at its top dead center. Thus, the mixture gas between these surfaces is squashed outward and squirts into the combustion chamber, when the piston is at top dead center.
Further, in order to increase overall combustion velocity, it is desirable that combustion of the mixture in the combustion chamber is initiated from a point which is as close to the three-diminisionally central part of the combustion chamber as possible, provided that no substantial radially unbalanced flow of gas such as due to squish exists in the combustion chamber.